A distal phalanx is a bone at the end of both the fingers and toes. Distal phalanges shape the nails of a human hand or foot and hence are also called ungula phalanges. It is not uncommon for them to be called terminal phalanges either in reference to the bones location at the end of the digits. The bones are shaped to support the finger. In humans, a distal phalanx is usually a flatter and wider bone compared to other mammals.
A phalanx that occurs at the end of human fingers is distinguishable by a mixture of flat and convex surfaces. The surface of a distal phalanx on a finger is horseshoe shaped so that it can support the flesh and vulnerable parts. Human fingers also contain apical tufts, which are wide openings that support the nail and finger.
A distal phalanx of the toe is usually very similar to that of the finger aside from a few small differences. Firstly, a toe distal phalanx is smaller than a finger phalanx. Also, the toe phalanges are flattened on the top and come with a larger end in order for them to fit and support the nail. They also have a large base that allows the bone to connect correctly to the second set.
Many mammals have similar distal phalanges although there are a large number of variations. For example, the apical tufts in other mammals can vary in size. This is thought to be an evolutionary response to the need for tool making. A human distal phalanx, however, is always larger than the phalanx of any other mammal.
Due to the distal phalanges close proximity to the end of the finger, injuries are likely. Distal phalanx fractures, for example, are very common and are often caused by the finger being crushed. In general a fracture to a distal phalanx won’t require surgical intervention although this depends on the severity of the injury. Immobilizing the phalanx for several weeks usually helps to ease the pain and allow for faster healing although isn’t always required.
Other potential injuries to a terminal phalanx include mallet finger, nail bed injuries and Jersey finger. The treatment for these injuries depends on the exact type as well as the severity of the problem. Immobilization is often used for a number of different types of injury though as this allows the joint a greater time to heal.